atari2600land's Blog

So score is an easy one... you have a couple of options. The first option, is if you have a minimum score, you can drop the least significant digits. For instance, if the smallest increment is 100 points, just add it as '1' and display the zeros fixed. That takes your (apparent) maximum from 32,767 to 3,276,700. The second thing you can do is use unsigned int instead of regular int - that will double your range and make the maximum 65535. These tips can be combined, of course.

 

Finally, if you need a truly larger range, then you can use 32-bits instead of 16-bits. If the compiler doesn't support "long" then just define two unsigned ints: "score_high" and "score_low" for instance. The easiest way to deal with this is a function that adds to the score for you (rather than adding inline). Then it can work transparently.

 

unsigned int score_low, score_high;

void addscore(int add) {

unsigned int oldlow = score_low;

score_low+=add;

if (score_low < oldlow) ++score_high;

}

[/core]

 

Most compilers will optimize out the 'oldlow' variable, which is just used to check if the score wrapped around. This works as-is only with unsigned ints - for signed ints it will wrap around to negative, so you would also need to fix up score_low.

 

That gives you the maximum 32-bit range (4,294,967,296), but it's a bit of a pain to display because you need to do a 32-bit division. So I like to cheat myself and make 'score_low' wrap at 10,000 instead. That way you can use your existing score display code - just display all 5 digits from score_high and the last 4 digits from score_low. In that case add_score looks like this:

 

[code]

unsigned int score_low, score_high;

void addscore(int add) {

score_low+=add;

if (score_low > 9999) {

score_low -= 10000;

++score_high;

}

}

[/core]

 

The bank-switching for larger games can be done manually too, but I haven't done it on Gameboy so I can't help much there.

 

Anyway, just rambling. Hope that's interesting.